Di Maria went off against West Brom but United are still to officially confirm the extent of his injury.Getty Images/Michael Regan

Manchester United winger Angel di Maria's fitness for the Premier League visit of Chelsea on Sunday has been plunged into further doubt as the club continues to delay confirming the extent of the Argentina international's thigh problem.

Di Maria was substituted after 76 minutes during the 2-2 draw with West Bromwich Albion on Monday and had ice applied to an upper thigh strain which saw him replaced by Ashley Young at The Hawthorns.

United manager Louis van Gaal did not comment on Di Maria's fitness during his numerous media commitments and an official line from the club regarding the record signing's injury prognosis is not expected until the scheduled press conference on Friday.

The 26-year-old has enjoyed a sparkling start to life in the Premier League, scoring three goals and making four assists, the latest coming as he set up Marouane Fellaini's first United goal against West Brom as the club's unbeaten run stretched to three games.

Having welcomed back Phil Jones and Ashley Young from injury, van Gaal can ill-afford another absentee, particularly given the fears surrounding the fitness of Ander Herrera, who was substituted at half-time on Monday.

Herrera missed three weeks of action with a fractured rib but returned from the start against West Brom, before going off at half time as he was replaced by Fellaini. Reports are suggesting the Spaniard faces another spell on the sidelines after aggravating the injury and will miss the visit of league leaders Chelsea.

Antonio Valencia, Paddy McNair, Jonny Evans, Jesse Lingard and Chris Smalling are all currently out injured, but Michael Carrick could make his first appearance of the season against Chelsea after he was an unused substitute against The Baggies. Captain Wayne Rooney is also absent through suspension.

Carrick suffered an ankle blow in the first week of pre-season training and is yet to play this season, the first of a myriad of injuries which have overshadowed the club's start to the campaign.

The visit of Jose Mourinho's side this weekend starts a difficult run of games for United which includes a trip to champions Manchester City and Arsenal before the end of November.